a {
  text-decoration: none;
}

.second-head {
  width: 100%;
  height: 60px;
  background-color: #F9F9F9;
  margin: 0 auto;
  border-bottom: 1px solid #ECECEC;
}

.second-head-div {
  width: 80%;
  height: 100%;
  /* background-color: blueviolet; */
  display: flex;
  justify-content: center;
}

.second-head-div div {
  width: auto;
  height: 57px;
  text-align: center;
  line-height: 57px;
  font-size: 16px;
}

.second-head-div div a {
  color: black;
}

.second-head-div div a:hover {
  color: blue;
}

.second-head-div div .border-div {
  width: 0px;
  height: 3px;
  background-color: blue;
}

.second-head-div div:hover .border-div {
  animation: bottomBorder 0.3s linear 0s;
  /*将动画最终结果保持*/
  animation-fill-mode: forwards;
}

@keyframes bottomBorder {
  0% {
    width: 0%;
  }
  100% {
    width: 100%;
  }
}